The character of Chachi is the younger cousin of Fonzie, first appearing in the television series Happy Days in 1977.[2] He eventually became a "heart throb" and love interest for the character Joanie Cunningham, with their relationship becoming a common theme for episodes.[3]

Chachi and Joanie moved off into the spinoff series Joanie Loves Chachi, when his mother Louisa and new stepfather Alfred "Al" Delvecchio, (the second owner of Arnold's) opened a new restaurant where Joanie and Chachi performed most of their music.[4]

Joanie and Chachi along with some of his cousins and a character named Bingo form a band, which is never named in the series.[5]

Joanie and Chachi returned to Happy Days when Joanie Loves Chachi was cancelled, and in the final Happy Days episode, Joanie and Chachi marry.

After his initial appearance, the character of Chachi was expanded to a recurring character due to positive reception by fans, with Baio receiving up to 5,000 fan letters a week.[2] When the writers began developing the character of Chachi as a musician, Baio was against the idea because he "didn't sing", but changed his mind based on the possibility of the fame associated with becoming a pop singer.[2] His catchphrase "wa, wa, wa" became popular with teenage girls.[2] However, an attempt to spark a fashion trend by having Chachi frequently costumed with a bandana tied around his pant leg did not catch on.[2]

The character was named after a street where the shows' creator Garry Marshall had lived.[2] There have been false rumors that circulated claiming that the broadcast of Joanie loves Chachi had high viewership numbers in Japan[6] or Korea because the name "Chachi" sounds like slang term for "penis" in those countries.[7]